AD75019

[Mauricio]

I´m trying to drive an AD75019 (16x16 Crosspoint Switch) with a PIC
Microcontroller) I have seen the SIN and SCLK waveforms with a scope
and everything seems to be right. But I can´t open or close any
switch. Has somebody some PIC working code in order to see what I´m
doing wrong?

Thanks in advance.

 

[Andrew Holme]

Mauricio wrote:

I´m trying to drive an AD75019 (16x16 Crosspoint Switch) with a PIC
Microcontroller) I have seen the SIN and SCLK waveforms with a scope
and everything seems to be right. But I can´t open or close any
switch. Has somebody some PIC working code in order to see what I´m
doing wrong?

Thanks in advance.

Are you shifting data in too fast or too slow? SCLK must be between 20 KHz
and 5 MHz.

Are you pulsing the PCLK parallel load after shifting the data in?

 

[Keith Wootten]

In message <4ad0a345.0501241256.2c3a7152@posting.google.com>, Mauricio
<mauricio.alvarez@gmail.com> writes

I´m trying to drive an AD75019 (16x16 Crosspoint Switch) with a PIC
Microcontroller) I have seen the SIN and SCLK waveforms with a scope
and everything seems to be right. But I can´t open or close any
switch. Has somebody some PIC working code in order to see what I´m
doing wrong?

I've done this - it was a few years ago and I no longer have access to
the PIC code. As I recall there's nothing particularly difficult *but*
the input shift register is dynamic and has a minimum clock speed of
(just looked it up) 20kHz. Once the switch configuration data is
clocked in, it's latched and needs no further concern.

Cheers
--
Keith Wootten

 

Hi andrew, thanks for reply.

Yes, I´m Shifting data at 250 KHz, and after shift all the 256 bits
I´m strobing the data with a low pulse at PCLK (width = 10uS)

Mauricio.

Andrew Holme wrote:

Mauricio wrote:
I´m trying to drive an AD75019 (16x16 Crosspoint Switch) with a
PIC
Microcontroller) I have seen the SIN and SCLK waveforms with a
scope
and everything seems to be right. But I can´t open or close any
switch. Has somebody some PIC working code in order to see what
I´m
doing wrong?

Thanks in advance.

Are you shifting data in too fast or too slow? SCLK must be between
20 KHz
and 5 MHz.

Are you pulsing the PCLK parallel load after shifting the data in?

 

1.- I´m injecting a square wave at analogue input, and viewing the
output with a scope.

2.- from the square wave generator.

3.- there are analog inputs unused but pulled down to ground

4.- It´s a PC ATX 300 Watts power supply.

5.- Setup timings seems to be right.

6.- I did a test software that run my PIC in an endless loop Writing
0x55 and SOUT is always High.


Andrew Holme wrote:

mauricio.alvarez@gmail.com wrote:
Hi andrew, thanks for reply.

Yes, I´m Shifting data at 250 KHz, and after shift all the 256
bits
I´m strobing the data with a low pulse at PCLK (width = 10uS)

How are you testing for switch closure?
How are you biasing the analogue inputs?
Are there any unused analogue pins? The datasheet doesn't say if
unused inputs are allowed - you might try high value SIL resistors to
GND.
What power supplies are you using?
Are you observing the correct setup and hold times (t1 & t3) as per
the
timing diagram on page 3 of the datasheet?

If you change your software to shift more than 256 bits - you should
see something coming out of SOUT - might be a useful test.

 

[Andrew Holme]

mauricio.alvarez@gmail.com wrote:

1.- I´m injecting a square wave at analogue input, and viewing the
output with a scope.
OK

2.- from the square wave generator.
What voltage levels w.r.t. ground?

3.- there are analog inputs unused but pulled down to ground
Directly or through resistors? What value?

4.- It´s a PC ATX 300 Watts power supply.
That's not what I meant. What are the voltages on Vdd, Vss and Vcc

relative to DGND.

5.- Setup timings seems to be right.
OK

Andrew Holme wrote:
If you change your software to shift more than 256 bits - you
should
see something coming out of SOUT - might be a useful test.

6.- I did a test software that run my PIC in an endless loop Writing
0x55 and SOUT is always High.

Something's wrong there.

 

[Keith Wootten]

In message <1106665782.119322.128290@f14g2000cwb.googlegroups.com>,
mauricio.alvarez@gmail.com writes

<snip>

6.- I did a test software that run my PIC in an endless loop Writing
0x55 and SOUT is always High.

Check that the clock is clocking continuously (at >20kHz) and manually
connect the Sin pin to 0V and 5V alternately while looking at Sout. Sout
should follow Sin (with a short delay). If it doesn't, you've probably
got a duff chip. Make sure the power supply sequences correctly, or use
Schottky diodes as suggested in the datasheet.

Cheers
--
Keith Wootten

 

[john jardine]

"Mauricio" <mauricio.alvarez@gmail.com> wrote in message
news:4ad0a345.0501241256.2c3a7152@posting.google.com...

I´m trying to drive an AD75019 (16x16 Crosspoint Switch) with a PIC
Microcontroller) I have seen the SIN and SCLK waveforms with a scope
and everything seems to be right. But I can´t open or close any
switch. Has somebody some PIC working code in order to see what I´m
doing wrong?

Thanks in advance.

This is a straight copy of a setup routine for a block of 8 of these chips
but shows that sending for say one chip, 80 bits of serial data, 80
clocks, and the final update strobe is perfectly straightforward.

regards
john

;---------------------------------------------------------------------------
---------------
DISABLE.THE.MATRIX.CHIPS
;shuts down all the outputs. Stops
'multi-output' self destruct
;sends out 640 '0's (0=disable out/pin.
1=enable it)
;this is a hardware routine only
ldw 80 ;640 bits worth of zeroes in one lump
wto scrap

local1 ldw 8 ;bit count each byte
wto scrap1

local2 matrixdata.low ;force zeroes into chips
matrixclock.high
matrixclock.low
decfsz scrap1,self
goto local2
decfsz scrap,self
goto local1

matrixupdate.low ;latch the data in to the 8 matrix chips
matrixupdate.high
RETURN ;having pumped 640 0's pumped out
;---------------------------------------------------------------------------
-----------------

 

[john jardine]

<mauricio.alvarez@gmail.com> wrote in message
news:1106687464.498527.203090@c13g2000cwb.googlegroups.com...
Thanks John.

This is a pretty nice code, but there are some things I don´t
undestand. Why must I load 640 zeroes into the shift registers if the
Crosspoint only have 256 switches? I can suppose you´re initializating
8 AD75019 connected in cascade, then my question is why only 80 bits
per IC? Please comment.

Mauricio, my apologies. Ignore my post. The code is for a AD8113 chip, which
is a 16X16 Video switcher.
[Having just said that I've looked at the AD75019 data sheet and noticed the
256 bits of data are serially loaded and latched the same way as the
AD8113].
regards
john

 

[malvarezdel]

Hi Andrew.

Square wave is 0 - 5V (5Vpp)

Vdd = +12V
Vss = -12V
Vcc = +5V

Pull down resistors 100K from each input to ground
Yes, something´s wrong here.

Regards